Solar Heat Panel

civil eggineer

I have a large (26'x40'), unattached, insulated garage that I heat above freezing in the winter time with two resistance electric heaters. I am contimplating on building some solar panels on the outside that are ducted into the garage to reduce my electric heat requirements. Does anyone have any personal experience with solar air heaters that they could pass along?

Cpt'n Cook

Are you talking about one of these home made heater boxes?

http://www.homeconstructionimprovement.com/solar-box-window-heater/

I have been thinking about making one for years.

civil eggineer

I am actually going to build them attached to the outside wall. Probably going to be about 7' wide and 8' tall. I also plan on using a thermostatically controlled fan to push the air through the collector when the heat builds up in the collector and is off when it is cloudy or night. I have seen a ton of designs but just wanted to hear from someone with one and what their overall thought is.

RGBHV

I have been contemplating adding some solar panels to the house - I'm interested to see where this post goes!

Michael

civil eggineer

The main thing I have noticed is when lexan or plexiglass panels are used they deteriorate quickly and become clouded. I salvaged some large glass panels 30 years ago from a motel remodel and finally realize why I salvaged them. My name is Tim and I am a pack rat!

[Deleted User]

YEA! Solar power... one of my pet interests.

Recently saw yet another Science Channel show on the Sun.

As a basic "metric", solar output was stated to be approx 1KW per square meter. Which works out to about 3400 BTU.

Forced air of course takes power, albeit MUCH less than a space heater.

If the panels are on an outside wall, could you not have a vent near floor that would "feed" the bottom of the panel, then as the sun heats up the air inside the panel, have an upper vent to vent the heated air into the room? Then you wouldn't even need forced air. Of course this only works while Sun is up.

edit: I see a "box" window heater was previously posted. The one above would probably have a smaller depth footprint (mountable in limited space or at heights), and could be wider than a window, and it would not necessarily require a window (roof mountable, with fan), but a window unit does have it's own set of advantages.

I believe the ancient Roman's used a similar technique to provide "air conditioning". A "chimney" on south facing wall, air inside heated by sun, rises, and creates a "draft". Then pipes set 6 ft underground, and entering the house, pulled in air and cooled it, all without any machinery.

http://www.thefarm.org/charities/i4at/surv/aircond.htm

An alternate approach might be to use a "coolant"/"liquid" based system where the heat can be concentrated and stored (like in a hot water heater) for use when the sun isn't up, like at night, when it is going to be colder, which is exactly when you'd want the room heated I would expect.

Of course there's always the Heliostat solution using liquid salt as the thermal storage medium. (Just kidding)

civil eggineer

To allow for a natural draft would require much larger openings which I am reluctant to do. A small blower consumes less energy then a single light bulb so I thought I would go that route at first. I am a little leary as solar power sounds good, I am not sure how reality meshes with its hype similar to wind power or ethanol. I will have to take a portion of siding off my garage so I hope it ends up making a significate reduction in my electric heater energy usage. Another thing easily overlooked is how many days are actually sunny compared to overcast.

[Deleted User]

Average sunshine by city:

http://www.ncdc.noaa.gov/oa/climate/online/ccd/pctposrank.txt

Yup, it would figure that the openings would have to be larger for natural draft. I suppose one solution (whole-out purist) would be a small PV solution to charge 12 V batteries and use them to run several
high-efficiency/high-volume 12 V fans in parallel with some kind of low-voltage thermostat. Of course all that depends on how much air volume (CFM) is needed.

Running it all at 12V (no inverter to 120VAC) I would think might make it simpler and more efficient (if you did PV for the fans).

My friend Michael had a wind turbine on his 43ft sailboat to help recharge the batteries. Noisy little sucker, but it did a good job, especially out in unobstructed water. Wind is VERY cool.

Humphrey Chimpden Earwicker

i used to make parabolic reflectors... no kidding. sad thing was i had to sit out in my front yard (only spot with sun) as the neighborhood kids rode by laffing on their bikes.

"cooked" a hamburger with it hahaha

met up 25 years later with one of my neighborhood buddies and he said, "you know, we made fun of you for that, but you were 11 or 12. i couldn't make one of them things TODAY if i had to". some measure of vindication.

one of the first programs i wrote for my DEC Pro350 was a thing that would solve andplot parabolic curves. used to used it to do my homework. hahaah

geek alert.

DEC Pro350. hahaha cost $15k in 1982 or so... had 1 meg of ram i think.

my mother worked for Dec, and I got it (free, on loan) as a trial. my first (and only) beta-testing job.

http://lordkalvan.vox.com/library/post/nablopomo---dec-professional-350.html

dbCooper

Hi st!ke,

I have very fond memories of working with DEC equipment back in the '80s. This write up on the PDP-8 might interest you....
http://www.grc.com/pdp-8/pdp-8.htm

Regards,
dbCooper

Humphrey Chimpden Earwicker

oh my... that's a little beyond me!

i remember the Pro had a few "emulators" and i think that was one.

we (my brother and I)used to dial in with a modem (1983!!) to DEC across town, but there wasn't much to do. we had to choose some computer to emulate in order to log on. don't remember the protocol exactly.

when i first saw wargames (where the kid dials in with a modem) i shrugged. not much of a hacker was I.

Essex County

I learned to program on a PDP-8L in the early 70s. We had to punch paper tape with our programs written in a long obsolete language called FOCAL.
Paul

Little Steven

Tim,

Problem is that with no storage system, liquid or battery, you have the heat when you need it least, sunny days.

Steve

Little Steven

Michael,

Hydro will pay you $.80 per KW/h hour generated and put back in the grid. We are going to cover the roof with them at work and install 1000w metal halide fixtures over them. Powered by the $.08 KW/h we buy. Not a real efficient transfer of energy but we will still make money. :laugh:

Steve

civil eggineer

I realize that but if it can cut down on the electric heaters running during sunny days, it should help. I normally only heat my garage to 40 degrees in the Winter so maybe with a decent rise in temp during the day from the solar collector, the carry over into the night will help there also.

[Deleted User]

Obviously I'm not familiar with your setup, is a "water wall" (or other thermal mass storage) worth considering?

I saw some stuff under the "Heat Storage" section of http://en.wikipedia.org/wiki/Passive_solar_building_design